Shear Bond Strength of a New High Fluoride Release Glass Ionomer Adhesive

Objective: To determine the shear bond strength of a new resin glass ionomer adhesive with higher fluoride release properties when bonding orthodontic brackets. Materials and Methods: Sixty freshly extracted human molars were collected and stored in a solution of 0.1% (weight/volume) thymol. The teeth were cleaned and polished. The teeth were randomly separated into three groups according to the enamel conditioner/etchant and adhesive used. Group I: 20 teeth conditioned with 10% polyacrylic acid and brackets bonded with the new glass ionomer adhesive. Group II: 20 teeth conditioned with 37% phosphoric acid and brackets bonded with the new glass ionomer adhesive. Group III (control): 20 teeth etched with 37% phosphoric acid and brackets bonded with a composite adhesive. Results: The results of the analysis of variance comparing the three experimental groups (F = 10.294) indicated the presence of significant differences between the three groups (P = .0001). The shear bond strengths were significantly lower in the two groups bonded with the new glass ionomer adhesive whether conditioned with polyacrylic acid (x̄ = 3.2 ± 1.8 MPa) or phosphoric acid (x̄ = 2.3 ± 1.1 MPa), while the mean shear bond strength of the composite adhesive was 5.2 ± 2.9 MPa. Conclusions: Although the increased fluoride release from the new glass ionomer has the potential of decreasing decalcification around orthodontic brackets, the shear bond strength of the material is relatively low.